System mailbox

The system mailbox is similar to a post office box: the post office delivers letters addressed to the person who owns that box.

Similarly, the system mailbox is a file where messages are delivered to a particular user. If the file does not exist when mail arrives, it is created. The file is deleted when all messages have been removed.

System mailboxes reside in the /var/spool/mail directory. Each system mailbox is named by the user ID associated with it. For example, if your user ID is karen, your system mailbox is: